Particle transport in intracranial aneurysms: a non-dimensional discrete element model study

Intracranial aneurysm (IA) haemodynamics is associated with low-velocity recirculating cavities that can promote or suppress the entry and near-wall approach of suspended microparticles. Here, we propose a proof-of-concept approach based on the interaction of mechanical particles with IA recirculating cavity haemodynamics, analysed via coupled Discrete Element Model - Computational Fluid Dynamics (DEM-CFD) simulations. An idealised IA model was first characterised in terms of velocity fields, wall shear stress (WSS), WSS gradients and vorticity, identifying maximal WSS and WSS gradient near the bifurcation tip where the aneurysm is located. The second part of the manuscript exploits the possibility to fulfill the cavity with particles with different sizes using their natural tendency to enter into low velocity areas Here, we investigated rods, discs, and spheres with two radii and densities, and interpreted their trajectories using a non-dimensional framework defined by five parameters: the convective Stokes number (S_tc), the sedimentation-to-convection ratio (S_v), the intra-saccular convection time (S_HV), the vortex-entrainment Stokes number (S_Ω) and the pulsatile Stokes number (St_ω). Particle entry through the neck increases markedly when S_tc approaches unity, reflecting strong inertia and limited ability to follow the flow curvature at the bifurcation apex; shape-dependent differences are linked to drag and shear lift in the neck region. In contrast, intra-sac penetration depth is promoted by low S_tc and S_Ω, which favour recirculating paths within the cavity, while S_v controls the vertical bias induced by settling or buoyancy. A regime map in the (S_tc, S_v) plane synthesises the behaviour of 28 particle configurations, framing particle transport as a non-dimensional problem and providing a rational basis to relate particle size, density and sphericity to the haemodynamic environment of a given aneurysm.